Open pdf document

Hi,
In my page have 2 portions,each contains seperate upload file controls. uploaded file name (.pdf)  will listed below to FileUpload control as link.
when click on those links will open that pdf file in browser.
My issue is when click on one link in first portion opning pdf doc fine. but when click on link in another portion will open a blank page.
In address bar path is correct.
Page look like,
Document Summary  | FileUpload Control |                                         Financial Report      | FileUpload Control | 

first.pdf                          & ...